Female patients presenting with persistent chest pain despite no obstructive coronary artery disease have impaired prognosis. Stress tests are often positive or inconclusive. As much as 20% of women with chest pain and minimal angiographic CAD have evidence of myocardial ischemia, suggesting impaired coronary microcirculation. The index of microvascular resistance (IMR) is a method for indirectly investigating microvascular function in the cardiac catheterization laboratory.